linux-kernel - Re: [PATCH] Forbid invocation of kexec_load() outside initial PID namespace

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Date:	Fri, 03 Aug 2012 06:07:36 -0700
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	"Daniel P. Berrange" <berrange@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Daniel Lezcano <daniel.lezcano@...e.fr>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] Forbid invocation of kexec_load() outside initial PID namespace

"Daniel P. Berrange" <berrange@...hat.com> wrote:

>On Fri, Aug 03, 2012 at 05:45:40AM -0700, Eric W. Biederman wrote:
>> The solution is to use user namespaces and to only test ns_capable on
>the magic reboot path.
>> 
>> For the 3.7 timeframe that should be a realistic solution.
>
>Hmm, that would imply that if LXC wants to allow reboot()/CAP_SYS_BOOT
>they will be forced to use CLONE_NEWUSER. I was rather looking for a
>way
>to allow the container to keep CAP_SYS_BOOT, without also mandating use
>of user namespaces.

If we remove the use of CAP_SYS_BOOT on the container reboot path perhaps.

But you have hit one small issue in the huge pile of issues why giving contaners capabilities is generally a bad idea.

This is the reason I have been insisting on a reasonable version of user namespaces for a long time.

When the security issues become important it is time for user namespaces.   That is their purpose.

Eric



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